One hand washes the other.
More German Proverbs:
Who carries doubtful people to his house, will doubtless from his carriage something lose.German
I would rather have a dog as a friend than an enemy.
German
Mind your own business.
German
Schnapps is schnapps and business is business.
German
No use in flogging a dead horse.
German
A nail secures the horse-shoe, the shoe the horse, the horse the man, the man the castle, and the castle the whole land.
German